This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-065255, filed Mar. 8, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a transmission apparatus, such as a radio telephone apparatus, and a transmission power detecting apparatus for detecting transmission power at such the transmission apparatus.
2. Description of the Related Art
FIG. 1 shows an arrangement of a radio transmitting section of a conventional radio telephone apparatus.
The radio telephone apparatus has a transmitting unit 1 and transmitting unit 2. The transmission frequency of the transmitting unit 1 is a predetermined frequency f1. The transmission frequency of the transmitting unit 2 is a predetermined frequency f2 higher than the frequency f1. The transmitting units 1 and 2 comprise modulators 1a and 2a, intermediate frequency band oscillators 1b and 2b, AGC amplifiers 1c and 2c, up-converters 1d and 2d, local oscillators 1e and 2e, bandpass filters 1f and 2f, and power amplifiers 1g and 2g, respectively.
The transmitting units 1 and 2 have their transmit operations controlled by a controller 3 to prevent both from simultaneously outputting their transmit signals. The transmit signals which are outputted from the transmitting units 1 and 2 are supplied, respectively through bandpass filters 4 and 5, to a diplexer 6 and then to an antenna 7 where each transmit signal is radiated.
In this type of radio telephone apparatus, it is necessary to monitor transmission power so as to, for example, control it. To this end, a transmission power detecting apparatus 8 is provided. The transmission power detecting apparatus 8 has power detectors (DET) 8a and 8b, a rectifying diode 8c and smoothing capacitor 8d. 
The power detectors 8a and 8b detect the power levels of outputting signals from the transmitting units 1 and 2. The power detectors 8a and 8b output detection signals representing the detecting power levels. Thus, the detection signal becomes an AC signal having its level varied in accordance with a variation in power level of the outputting signals from the transmitting units 1 and 2.
The output terminals of the power detectors 8a and 8b are connected to the anode of the rectifying diode 8c. An output terminal T is connected to the cathode of the rectifying diode 8c, and the cathode of the rectifying diode 8c is grounded through the smoothing capacitor 8d. Thus, the detection signal outputted from either of the power detectors 8a and 8b is converted to a DC voltage by the rectifying diode 8c and smoothing capacitor 8d and outputted from the output terminal T.
In such transmission power detecting apparatus 8, the transmitting units 1 and 2 perform no simultaneous transmit operation and, by utilizing this, a DC voltage conversion circuit is shared, the DC voltage conversion circuit comprising the rectifying diode 8c and smoothing capacitor 8d. By doing so, the circuit size is made smaller.
Incidentally, if the transmission power detecting apparatus 8 is so configured as set out above, a portion of the output signal of one of the transmitting units flows into the other transmitting system, thus producing a waste loss. As a result, the transmission power becomes smaller.
Further, there is sometimes the case where, depending upon a relation between the frequencies f1 and f2, a high harmonic wave of one frequency occupies the same frequency band of the other frequency. In this case, there is a risk that the high harmonic wave flows into said other transmitting system will be supplied through the bandpass filter 4 or bandpass filter 5 to the antenna 7 and a high harmonic component will be radiated.
The object of the present invention is to provide an apparatus which has a simple structure and can yet prevent transmitting systems from flowing unnecessary signals from one the other.
According to one aspect of the present invention, there is provided a transmission power detecting apparatus used for a transmission apparatus having a plurality of transmitting units with each transmission unit performing no simultaneous transmit operation relative to a remaining transmitting unit and adapted to detect a transmission power at the output of the transmission unit, comprising a plurality of detectors each configured to output a detection signal corresponding to an output power of a corresponding one of the transmitting units; a plurality of rectifiers each configured to receive an output of the corresponding detector at an input terminal and to allow a flow of only electric current from the input terminal toward an output terminal; and a smoothing device configured to smooth a signal supplied to one input terminal to which output terminals of the rectifiers are connected.
According to another aspect of the present invention, there is provided a transmission apparatus comprising a plurality of transmitting units each configured to perform no simultaneous transmit operation relative to a remaining transmitting unit; a plurality of detectors each configured to output a detection signal corresponding to an output power of the corresponding one of the transmitting units; a plurality of rectifiers each configured to receive an output of the corresponding detector at an input terminal and to allow only electric current from the input terminal toward an output terminal; a smoothing device configured to smooth a signal supplied one input terminal to which the output terminals of the rectifiers are connected; and a controller configured to control transmission power of the transmitting unit, which is performing the transmit operation, on the basis of a signal smoothed by the smoothing device.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.